Physical Properties of Hydrogen
Hydrogen (H) is the only chemical element in the periodic table in which valence orbital electron under the direct influence of the nucleus or there is no shielding electron with the symbol ‘H’ and molecular formula H2. In learning chemistry or chemical science, hydrogen gas molecule (molar mass or molecular weight = 2.016 g/mol) is a colorless, odorless, tasteless, flammable substance uses at the earliest time for the production of water.
Atomic hydrogen gas has a very simple structural model that contains one electron and one proton with atomic number = 1 and atomic weight or mass = 1.007829. Under ordinary conditions, due to the presence of one valence electron in 1s-orbital, the gaseous atoms make a wide number of common chemical bonding like covalent, ionic, bridge bond, and hydrogen bonding.
Discovery and Isotopes
In 1766 Henry Cavendish, an English chemist and physicist discovered the most combustible element or molecule like hydrogen gas, and the name was given from the origin of Greek words meaning ‘water maker’. Hydrogen has three most common isotopes having the chemical name protium (1H1), deuterium (1H2), and tritium (1H3) form three covalent gas molecules like dihydrogen, dideuterium, and ditritium which uses as an alternative fuel cell for engine or renewable energy sources for our environment.
Besides the common physical state of matter like solid, liquid, and gas on the earth’s universe, hydrogen is a gas molecule at room temperature and the third most abundant chemical element after oxygen and silicon and 2nd most abundant gas molecule after oxygen.
Position in Periodic Table and Bonding
The ns1 electronic configuration hydrogen justifies the position in period-1 and group-1 with the alkali metals family (lithium, sodium, potassium, rubidium, cesium, and francium) with very low ionization energy. Consider the other chemical facts, the electron configuration formula of hydrogen is just one electron short of the next noble gas helium and may be placed in group-17 with the halogen family (fluorine, chlorine, bromine, iodine) that has very high electronegativity and electron affinity. Due to the presence of the half-filled valence electrons, hydrogen also placed group-14 with the carbon family by forming a wide number of covalent chemical bonds with a wide range of polarity. The most common oxidation number of hydrogen = +1, but due to unique characteristics, it also shows -1 oxidation state to form LiH, NaH, CsH, CaH2 compounds.
Chemical Properties of Atomic Hydrogen
Hydrogen is the most abundant and unique type of chemical element that does not found free in the earth’s atmosphere and widely uses in everyday life. Because the kinetic energy at the earth’s temperature is sufficient to escape from the earth’s gravitational energy to decreasing the density of the hydrogen gas molecule. The molecular hydrogen is a very stable and nonreactive species due to high bond energy but the atomic form is the most reactive species, and only one percent of atomic forms are present in the H2 gas molecule.
The half-life of the atomic form nearly 1 second at 0.2 mm pressure and huge specific heat uses for recombination about 432.6 kJ mol-1. Therefore, this process uses for high-temperature welding of metals tantalum and tungsten. Due to high reactivity, the atom functions as a strong reducing agent that reduces different types of common chemical compounds like ethylene, acetylene, hydrogen peroxide, and metal ions. Hydrogen atom absorbed energy to shift their valence electrons particles to different energy levels. The electrons in higher energy levels are relatively unstable and hence drop back to the lower energy level to produce the electromagnetic spectrum.
Nuclear Spin Isomers
When the nucleus of an atom contains an odd number of nucleons, the nucleus has a resultant spin. If such two atoms combine to form the diatomic molecule the nuclei may have parallel or anti-parallel spins. This is called nuclear spin isomerism. The molecule in which the two nuclei have a parallel spin is called ortho-isomer. But the molecule with antiparallel nuclear spins called para-isomer. Such nuclear spin isomer found in H2, D2, T2, N2, O2, etc. The conversion of para-H2 to the ortho-H2 compound or vice versa is normally very slow. They involved the forbidden transition between two energy states of the different spin municipalities.
Uses of Molecular and Atomic Hydrogen
- Atomic element and molecular hydrogen compound widely used in the different types of fuel cells for the energy generator process or different industrial production and pH scale determination for the neutral, base, and acid solution.
- Hydrogen gas uses for the generating of ammonia molecules, an important chemical compound for industrial chemical plants uses for the formation of compounds like hydrochloric acid, sulfuric acid, nitric acid, methyl alcohol, etc. Methyl alcohol prepared from hydrogen subsequently oxidized by the oxo to formaldehyde uses for the synthesis of plastics.
- In hydroformylation reaction or the addition of H2 and formyl group into unsaturated hydrocarbon like alkenes. The produced aldehydes subsequently changed to alcohol. These are uses for the preparation of PVC resin and detergents.
- Hydrogen atom or H2 molecule is used for welding high melting or boiling point metals like tantalum and tungsten, reduction of metal oxides. A direct reduction of iron ore was developed on a commercial basis for the preparation of iron metal.
- The liquid hydrogen molecule is used in the population of rockets and bubble chambers. Hydrogen oxygen type mixture uses in the fuel cells for the production of renewable energy or importance in the powered generation process of electric vehicles.
- The hydrogen spectrum is used to define different types of physical or chemical properties like molecular formula or structure, chemical bonding, etc.
Uses of Protium Deuterium and Tritium
Deuterium oxide or D2O is largely used as heavy water in nuclear power plants. D2O is also used as a source of deuterium compounds. Therefore the most common isotopes of hydrogen gas look like deuterium used to study the physical and chemical properties like kinetics reaction mechanism and reaction order determination. Titanium is widely used as a tracer element due to its radioactivity. Tritium extensively uses hydrological studies to the moment of groundwater in the earth’s environment, to study the absorption of crystalline metals and multiphase alloys in autoradiography. In learning chemistry, hydrogen uses to define the reaction mechanism, find the kinetics of the chemical reaction, and common catalysis properties.